I just collected a good size Decorator Crab or 'Sponge Crab' while at the beach the other day. It has a big white with orange spots tunicate covering it's carapace. I was a bit unsure about it because it is fairly big, about the size of a silver dollar. Also I was unsure of it's eating habits. But I have a local only tank and it could always go in there. However, I put it in my display refugium and it immediately started working on some of the hairy algae I've had an issue with. Over the last 2 days that's all we've seen it do as it goes from one place to another checking out the algae. It might be a bulldozer in a tank full of small corals and frags, but in my display refugium it is a perfect new house guest!
I was surprised at how fast it can get around in the tank and then this morning I walked up to the tank and it was at the upper tip of a 16" tall Gorgonian and it jumped off and gently floated down to the sand. The tunicate on it's back has been hollowed out so it fits perfectly. And they have hooks on their back legs that hold onto it. So when it jumped, the tunicate opens up a bit at the front and works like a parachute for the ride down to the sand!